bact growth: physical and chemical requirements

Question 1

what is bacterial growth?

Answer 1

increase in the NUMBER of cells and not the size of cells

Question 2

how do bacteria multiply?

Answer 2

binary fission (asexual)

Question 3

what is generation time?

Answer 3

time required for one cell to become two cells

Question 4

what are the two measurements of bacterial growth?

Answer 4

direct method

indirect method

Question 5

what is the direct method of measuring bacterial growth?

Answer 5

• microscopic counts

- viable counts

Question 6

what is microscopic counts?

Answer 6

both live and dead cells are counted (total cell count)

Question 7

what are viable counts?

Answer 7

only live cells are counted

Question 8

what is serial dilution?

Answer 8

in viable counts: samples are diluted, generally 10-fold, to be counted

Question 9

what are indirect methods of measuring bacterial growth?

Answer 9

• measure turbidity in a spectrophotometer

- absorbance or optical density

Question 10

what are the four phases of bacterial growth on the growth curve?

Answer 10

lag, log, stationary, death

Question 11

what are the physical requirements of bacterial growth?

Answer 11

oxygen, CO2, temperature, pH, and osmotic pressure

Question 12

what are the chemical requirements of bacterial growth?

Answer 12

nutrients

Question 13

what are the 3 types of aerobes?

Answer 13

-obligate
-facultative
microaerophilic

Question 14

what is the relationship to O2 and type of energy metabolism of obligate aerobes?

Answer 14

• required

- aerobic respiration

Question 15

what is the relationship to O2 and type of energy metabolism of facultative aerobes

Answer 15

• O2 not required by better growth with O2

- aerobic respiration and fermentation

Question 16

what is the relationship to O2 and type of energy metabolism of microaerophillic aerobes?

Answer 16

• O2 required but at a lower concentration

- aerobic respiration

Question 17

what is the relationship to O2 and type of energy metabolism of aerotolerant anaerobes?

Answer 17

• O2 not required

- fermentation

Question 18

what is the relationship to O2 and type of energy metabolism of obligate anaerobes?

Answer 18

• O2 not required, its harmful

- fermentation

Question 19

what are the toxic forms of oxygen

Answer 19

• singlet oxygen
• superoxide oxygen
• peroxide anion
• hydroxy radical

Question 20

how do toxic forms of oxygen inhibit or kill bacteria?

Answer 20

by disrupting nucleic acid and protein structures

Question 21

what 3 enzymes detox oxygen radicals?

Answer 21

• catalase
• peroxidase
• superoxide dismutase

Question 22

what is required for biosynthesis?

Answer 22

carbon dioxide

Question 23

what bacteria thrives in temps 10 to 15 C?

Answer 23

psychrophiles

Question 24

what bacteria thrives in temps 30 to 37 C

Answer 24

mesophiles

Question 25

what bacteria thrives in temps >55 C

Answer 25

thermophiles

Question 26

what is the optimal physiological pH?

Answer 26

6.8-7.2

Question 27

are fungi bothered by pH?

Answer 27

no, they are acid tolerant

Question 28

what is the physiological ionic strength?

Answer 28

0.65% NaCl

Question 29

2 requirements for chemical growth

Answer 29

carbon and energy

Question 30

carbon required for chemical growth

Answer 30

CO2 and organic

Question 31

energy requirements for chemical growth

Answer 31

light or chemical

Question 32

pathogens have what chemical requirements for growth?

Answer 32

organic molecules for energy and carbon

Question 33

nutrient requirements: macronutrients

Answer 33

carbon, nitrogen (others like S, K, P, Na, Ca etc)

Question 34

nutrient requirements: micronutrients

Answer 34

Metals (Cu, Ze, Fe, Mn, Mo, etc)

Question 35

what metal plays a major role in respiration?

Answer 35

iron

Question 36

host Fe is tied up to what proteins?

Answer 36

transferrin and lactoferrin

Question 37

what are siderophores?

Answer 37

- iron-binding agents produced by bacteria - enterobactins (E. coli and Salmonella) - bind to Fe and transport to cell

Question 38

what is culture medium?

Answer 38

nutrient solution required for growth - liquid (broth) - solid (agar)

Question 39

what is inoculum?

Answer 39

bacterial cells to the medium to initiate growth

Question 40

what is culture?

Answer 40

bacterial growth in a medium

Question 41

what is a defined medium?

Answer 41

exact chemical composition is known, pure chemicals are used

Question 42

what is a complex medium?

Answer 42

chemical composition is not know. has complex substances

Question 43

what is a general purpose medium?

Answer 43

allows growth of most bacteria

Question 44

what is a selective medium?

Answer 44

suppresses growth of unwanted bacteria and promotes growth of desired bacteria

Question 45

what is enrichment medium?

Answer 45

a liquid medium designed to increase growth of a desired bacteria

Question 46

what is differential medium?

Answer 46

differentiates two or more types of bacteria. -generally a solid medium